I spent a long time thinking I was being dramatic about weather until I actually started writing it down, and the pattern was real. Sharing the physiology because it helped me stop feeling crazy about it.

Heat and humidity are the clearest. Regulating temperature is an autonomic job, so when you overheat your skin vessels open up and you sweat, which pools blood and pulls fluid out of an already low blood volume. Humidity is the sneaky part: sweat only cools you when it evaporates, and muggy air is already full of water, so a humid 78 degree day can wreck me worse than a dry 88.

Barometric pressure is fuzzier. The evidence is more mixed than for heat, but a lot of us feel the day before a storm, and the likely reason is that a front doesn't just change pressure, it swings temp and humidity at the same time. Cold is genuinely split: some people feel their best in winter because vessels tighten and blood centralizes, others get hammered by Raynaud's and the dry heating.

The thing that actually helped was logging a one-word weather note next to my heart rate and how standing felt, so I could tell a real trigger from a coincidence instead of trusting my memory. Not medical advice, just a fellow patient, and I bring the patterns to my doctor. 

Weather and POTS: How Barometric Pressure, Humidity, and Cold Shift Your Symptoms